Abstract: There is provided a non-contact IC card having a power supply circuit capable of stably receiving power even if power consumption is varied after the power supply object circuit is switched to normal operation. The non-contact IC card includes: an antenna (11) for receiving an electromagnetic wave, a rectifier circuit (12) for rectifying AC current generated from the electromagnetic wave received by the antenna (11), a regulator (13) for regulating DC voltage VIN outputted from the rectifier circuit (12), a control circuit (15) for receiving power from the regulator (13) and executing a predetermined function, and a voltage detection circuit (14) for detecting the output voltage VIN of the rectifier circuit (12). According to the result of detection of the output voltage VIN from the rectifier circuit (12), the voltage detection circuit (14) resets or releases reset of the control circuit (15).

Abstract: A transmitter apparatus has a modulator for modulating a carrier wave to produce a modulated wave having communication data superimposed thereon and a transmitter for transmitting the modulated wave to a receiver apparatus. Before starting communication, the transmitter apparatus transmits a predetermined dummy pulse to the receiver apparatus so as to bring the communication data restored by demodulation in the receiver apparatus into a logic state in which the communication data should be kept when no communication is taking place. This makes it possible to perform correct communication even if the communication data demodulated in the receiver apparatus before the start of communication is not kept in the logic state in which it should be kept when no communication is taking place.

Abstract: When a built-in nonvolatile memory in a microcomputer is tested, a control program prestored in a boot ROM is run upon entering a test command from an external communication device; a test program is transferred from the external communication device to a built-in RAM through a communication circuit; a control of a CPU is switched to the built-in RAM after the test program has been transferred and a test is conducted on the nonvolatile memory; and a test result and a fail log are transferred to the external communication device through the communication circuit. Consequently, the built-in nonvolatile memory in the microcomputer can be checked without leaving the test program on the chip.

Abstract: An electromagnetic coupling characteristic adjustment method for adjusting an electromagnetic coupling characteristic between a reader/writer device and an IC card which are used in a non-contact communication system in which a power transmission antenna coil provided in the reader/writer device and a power receiving antenna coil provided in the IC card are electromagnetically coupled so that the reader/writer device supplies power to the IC card without contact with the IC card. The power supply device includes adjustment impedance elements respectively connected in series and in parallel with the power transmission antenna coil. Impedances of these adjustment impedance elements are determined so that the semiconductor device receives greatest power when a power supply distance, which is a distance between the power transmission antenna coil and the power receiving antenna coil, has a predetermined value not less than 0.

Abstract: An electromagnetic coupling characteristic adjustment method for adjusting an electromagnetic coupling characteristic between a reader/writer device and an IC card which are used in a non-contact communication system in which a power transmission antenna coil provided in the reader/writer device and a power receiving antenna coil provided in the IC card are electromagnetically coupled so that the reader/writer device supplies power to the IC card without contact with the IC card. The power supply device includes adjustment impedance elements respectively connected in series and in parallel with the power transmission antenna coil. Impedances of these adjustment impedance elements are determined so that the semiconductor device receives greatest power when a power supply distance, which is a distance between the power transmission antenna coil and the power receiving antenna coil, has a predetermined value not less than 0.

Abstract: A power-on reset circuit includes a first reset circuit, a second reset circuit, and an NOR circuit. The first reset circuit detects VCC2V supplied to a logic section so as to produce a first reset signal RST1, and the second reset circuit detects REGIN voltage, which is an output voltage of a rectifying circuit that rectifies power voltage obtained from an external power supply source, so as to produce a second reset signal RST2. The NOR circuit outputs either the RST1 or the RST2 as a reset signal P-RST. The above arrangement can provide the power-on reset circuit which outputs a reliable and effective reset signal even in case where the rising of power obtained from the external power supply source varies.

Abstract: A transmitter apparatus has a modulator for modulating a carrier wave to produce a modulated wave having communication data superimposed thereon and a transmitter for transmitting the modulated wave to a receiver apparatus. Before starting communication, the transmitter apparatus transmits a predetermined dummy pulse to the receiver apparatus so as to bring the communication data restored by demodulation in the receiver apparatus into a logic state in which the communication data should be kept when no communication is taking place. This makes it possible to perform correct communication even if the communication data demodulated in the receiver apparatus before the start of communication is not kept in the logic state in which it should be kept when no communication is taking place.

Abstract: A power-on reset circuit includes a first reset circuit, a second reset circuit, and an NOR circuit. The first reset circuit detects VCC2V supplied to a logic section so as to produce a first reset signal RST1, and the second reset circuit detects REGIN voltage, which is an output voltage of a rectifying circuit that rectifies power voltage obtained from an external power supply source, so as to produce a second reset signal RST2. The NOR circuit outputs either the RST1 or the RST2 as a reset signal P-RST. The above arrangement can provide the power-on reset circuit which outputs a reliable and effective reset signal even in case where the rising of power obtained from the external power supply source varies.